Audio routing for an automobile

ABSTRACT

An audio signal processing system for a vehicle is disclosed. The vehicle has a plurality of audio output producing devices. The system includes an audio input circuit, a processor, an audio output circuit, and at lease one speaker. The audio input circuit receives a plurality of audio signals from the plurality audio output producing devices. The processor is in communication with the audio input circuit for combining the plurality of audio signals. The audio output circuit is in communication with the audio input circuit for receiving the combined plurality of audio output signals. The audio output circuit conditions the plurality of audio signals for output. The at least one speaker broadcasts the conditioned plurality of audio signals to a vehicle occupant.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present invention claims priority to U.S. Provisional SerialNo. 60/341,095, filed Oct. 29, 2001, entitled “Audio Routing For AnAutomobile.”

TECHNICAL FIELD

[0002] The present invention relates to systems and methods for routingaudio signals in an automobile and for allowing multiple audio signalsto be broadcasted over a single set of speakers.

BACKGROUND

[0003] A typical emergency services vehicle today has numerous devicesthat use audio inputs and generate audio outputs. They include two-wayradios, scanners, AM/FM radios, PA systems, Doppler radar tones,computer input and output, etc. In most cases each piece of equipmentthat generates output will have its own speakers and each piece ofequipment that requires input will have its own microphone.

[0004] The proliferation of speakers and microphones (and often theequipment to which they are attached) in the passenger compartment leadsto clutter and confusion. The audio outputs are not coordinated witheach other, so a low priority output might drown out a high priorityoutput. Similarly, it may be difficult to locate the correct microphonefor a particular device.

[0005] One of the reasons that vehicles may have multiple two-way radiosis that different emergency services may communicate on different bands,thus requiring a separate radio for each service. A consequence of thisis that when several emergency services arrive at a site, they may notall be able to talk to each other. The situation is exacerbated when theworkers leave their vehicles and carry handheld radios, which typicallyservice a single band each.

[0006] Large agencies have command vehicles that contain specializedequipment (repeaters) to receive signals on one band and retransmit themon another. These vehicles are deployed to sites as needed, to allow thedifferent services to communicate with each other.

[0007] Therefore, what is needed is a system and method for anautomobile that integrates all of the audio signaling, and eliminatesredundant speakers and microphones. The system and method should alsoallow any vehicle to become a repeater using two-way radios alreadypresent.

SUMMARY

[0008] In an aspect of the present invention an audio signal processingsystem for a vehicle is provided. The vehicle has a plurality of audiooutput producing devices. The system includes an audio input circuit, aprocessor, an audio output circuit, and at lease one speaker. The audioinput circuit receives a plurality of audio signals from the pluralityaudio output producing devices. The processor is in communication withthe audio input circuit for combining the plurality of audio signals.The audio output circuit is in communication with the audio inputcircuit for receiving the combined plurality of audio output signals.The audio output circuit conditions the plurality of audio signals foroutput. The at least one speaker broadcasts the conditioned plurality ofaudio signals to a vehicle occupant.

[0009] In another aspect of the present invention the audio inputcircuit further comprises a plurality of analog to digital converters.

[0010] In yet another aspect of the present invention the audio inputcircuit further comprises a plurality of CODECS.

[0011] In yet another aspect of the present invention the audio inputcircuit comprises twenty CODECS.

[0012] In still another aspect of the present invention the processorfurther comprises a digital signal processor.

[0013] In still another aspect of the present invention the systemfurther comprises four speakers.

[0014] In still another aspect of the present invention the systemfurther comprises at least one microphone.

[0015] In yet another aspect of the present invention the audio outputcircuit further comprises an audio amplifier.

[0016] In yet another aspect of the present invention the audio inputcircuit further comprises a microphone router circuit for directing aplurality of microphone inputs to a plurality of audio equipment.

[0017] In still another aspect of the present invention the audio outputcircuit further comprises an audio mixer for receiving the plurality ofaudio signals and directing the plurality of audio signals to the properoutput device. In yet another embodiment of the present invention, theaudio mixer functions is a repeater by receiving audio signals havingdifferent frequencies and outputting an audio output signal having asingle frequency.

[0018] In yet another aspect of the present invention an audio signalprocessing system for a vehicle is provided. The vehicle has a pluralityof audio output producing devices. The system includes an audio inputcircuit, a processor, a voice activated control circuit, an audio outputcircuit, and at lease one speaker. The audio input circuit receives aplurality of audio signals from the plurality audio output producingdevices. The processor is in communication with the audio input circuitfor combining the plurality of audio signals. The voice activatedcontrol circuit in communication with the processor for controlling aprocessor operation. The audio output circuit is in communication withthe audio input circuit for receiving the combined plurality of audiooutput signals. The audio output circuit conditions the plurality ofaudio signals for output. The at least one speaker broadcasts theconditioned plurality of audio signals to a vehicle occupant.

[0019] In yet another aspect of the present invention a method forprocessing audio signals for broadcasting in a vehicle is provided. Thevehicle has a plurality of audio output producing devices. The methodincludes receiving a plurality of audio signals from the plurality ofaudio output producing devices, combining the plurality of audio signalsusing a processor, receiving the combined plurality of audio outputsignals using an audio output circuit, wherein the audio output circuitconditions the signals for output, and broadcasting the conditionedplurality of audio signals to a vehicle occupant using at lease onespeaker.

[0020] These and other aspects and advantages of the present inventionwill become apparent upon reading the following detailed description ofthe invention in combination with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

[0021]FIG. 1 is a schematic diagram illustrating a vehicle having anaudio board for mixing and broadcasting audio signals, in accordancewith the present invention;

[0022]FIG. 2 is a schematic diagram illustrating the connection of amicrophone (not shown) to the mixer busses, in accordance with thepresent invention;

[0023]FIG. 3 is a schematic diagram illustrating the connection of amonaural input to the mixer busses, in accordance with the presentinvention;

[0024]FIG. 4 is a schematic diagram illustrating the connection of thestereo input to the mixer busses, in accordance with the presentinvention;

[0025]FIG. 5 is a block diagram illustrating the microphone router, inaccordance with the present invention;

[0026]FIG. 6 is a schematic diagram illustrating a microphone inputcircuit, in accordance with the present invention;

[0027]FIG. 7 is a schematic diagram illustrating a microphone routercircuit for matching router and output circuits, in accordance with thepresent invention;

[0028]FIG. 8 is a block diagram illustrating an embodiment of the audioboard, in accordance with the present invention;

[0029]FIG. 9 is an alternate embodiment illustrating an in vehicle audiosystem for processing a plurality of audio input signals, in accordancewith the present invention;

[0030]FIG. 10 is a block diagram illustrating a general purpose inputchannel, in accordance with the present invention;

[0031]FIG. 11 is a block diagram illustrating an audio routing logic foran output channel, in accordance with the present invention;

[0032]FIG. 12 is a block diagram illustrating how the PTT signal foreach output is generated, in accordance with the present invention; and

[0033]FIG. 13 is a block diagram illustrating an audio routing for asingle output channel, in accordance with the present invention.

DETAILED DESCRIPTION

[0034] With reference to FIG. 1, a vehicle 10 having an audio board 12for mixing and broadcasting audio signals is provided, in accordancewith the present invention. The audio board 12 includes an audio mixer14 for combining audio signals for delivery to the user and otherequipment, and a microphone router for directing the microphone inputsto the equipment that uses them.

[0035] The audio board 12 further includes a microphone router 16.Microphone router 16 and audio mixer 14 are both under the control of aprocessor 17 such as a MPC-565. The microphone router directs microphoneinput from either an array microphone or the hand-held microphone to theappropriate piece of equipment (e.g., a radio transmitter or the voicerecognition system (VACM) 20). The audio mixer 14 takes all of theavailable audio signals (radios 22, microphones, voice feedback, etc.)and directs them to the proper output devices (e.g., speakers 24 in thevehicle or the PA speaker (not shown)). Additionally an application'sprocessor 19 in communication with audio mixer 14 is a source of audiosignals and communicates the audio signals to audio mixer 14. AP 19 is aWindows' based computer system for hosting Windows' applications.

[0036] Further, the audio mixer 14 receives audio from a variety ofdevices in the vehicle and routes them to speaker 24, PA, and anoptional recording device 26. The audio mixer 14 is, in an embodiment ofthe present invention, a 15 input×3 output switch. In principle it couldroute any mix of input signals to any combination of output ports.

[0037] The mixer handles three kinds of inputs: monaural microphoneswith push-to-talk (PTT) signal, other monaural inputs (without PTT), andstereo inputs. The monaural and stereo inputs can be either line levelor speaker level signals. TABLE 1 Signal Purpose Type 1 Output fromradio (AM/FM tuner, voice feedback stereo from VACM, etc.) 2 APsound/voice stereo 3 general purpose (two-way radio, scanner, etc.)monaural 4 general purpose monaural 5 general purpose monaural 6 generalpurpose monaural 7 general purpose monaural 8 general purpose monaural 9general purpose monaural 10 general purpose monaural 11 general purposemonaural 12 general purpose monaural 13 microphone 1 microphone 14microphone 2 microphone 15 microphone 3 microphone

[0038] The mixer 14 delivers three outputs: (1) for a stereo speakeramplifier 28, (2) for the PA amplifier, and (3) for an optionalrecording device 26. Table 2, below, shows an assignment of the outputsignals, in accordance with an embodiment of the present invention.TABLE 2 Signal Purpose Type 1 power amplifier to vehicle speakers stereo2 PA system monaural with PTT 3 optional recording system monaural

[0039] Internally mixer 14 in an embodiment of the present invention,has three output busses: (1) a Stereo bus—a left and a right audiochannel, (2) Aux (auxiliary) bus—a monaural audio channel, (3) PA(public address) bus—a monaural audio channel and a push-to-talk signal.

[0040] There are 15 input lines that connect to the busses, undercomputer control. The input lines are partitioned into three microphoneinputs, ten monaural inputs, and two stereo inputs. Each of the threekinds of input connects to the busses differently, and delivers aslightly different set of capabilities.

[0041] As shown in FIG. 1, note that the audio outputs of the radiosfeed back into the microphone router, so that output from one radio canbe fed back into another radio, thus accomplishing the repeaterfunction.

[0042] With reference to FIG. 2, the connection of a microphone 18(shown in FIG. 1) to mixer 14 busses is illustrated, in accordance withthe present invention. Microphone 30 can be routed to the Aux 32 and PA34 busses. The microphone should not be routed to stereo bus 36.Further, the PTT signal routing is shown as a relay 38 in FIG. 2.However, the PTT signal routing could equally well be implemented as asolid-state switch.

[0043] With reference to FIG. 3, the connection of a monaural input 33to the mixer busses is illustrated, in accordance with the presentinvention. The monaural signal can be routed to all three busses 32, 34and 36. By changing the relative volume of the signal on the left andright stereo channels, the mixer can pan the signal from left to right.

[0044] Each monaural input has two mechanically configured settings.First the input signal can be either line level 35 or speaker level 37.Second, a push-to-talk signal 41 can either be supplied directly by theinput device or a computer controlled squelch circuit in the mixer cangenerate it. The settings are implemented as either a DIP switch or ajumper. A computer controlled solid-state switch may also be used.

[0045] With reference to FIG. 4, the connection of the stereo input 40to the mixer busses 32, 34, 36 is illustrated, in accordance with thepresent invention. The stereo input 40 can be routed to the stereo 36and aux 32 busses. The stereo inputs are intended for a vehicleentertainment system (i.e. an AM/FM tuner) which are not required to berouted to the PA bus 24.

[0046] The mixer can change the balance of the stereo output, and canmix the right and left channel inputs together on both the right andleft channel outputs. This allows both reducing the channel separationand steering the apparent location of the signal.

[0047] Each stereo input 40 has a configuration setting 42 to switchbetween speaker 44 and line level 46 inputs. It is implemented similarlyto the settings for a monaural input.

[0048] The microphone router occupies three microphone inputs and sendsthe audio and PTT signals to the VACM (for voice recognition) and up tofive radios or other devices. The router routes both audio and PTTsignals. The PTT enables the microphone and the appropriate outputdevices.

[0049] The microphone router can send any input to one of the sixoutputs. Any inputs not being used are disabled. Multiple microphonescan be routed to the same output. Routing more than one microphone tothe same output causes them to mix (i.e., the audio is mixed and the PTTsignals are OR'd together) and both can talk at the same time.

[0050] The three microphones are preferably configured as follows:

[0051] 1. a hands free microphone for the driver;

[0052] 2. an optional handheld microphone for driver or passenger; and

[0053] 3. an optional auxiliary microphone (possibly a wirelessmicrophone).

[0054] In addition to the switched output, the router provides anunswitched buffered output from each microphone that is sent as an inputto the audio mixer.

[0055] With reference to FIG. 5, a block diagram of the microphonerouter 50 is illustrated, in accordance with the present invention. Theswitch is implemented using 1:8 demultiplexers 52 of which one output is“unused” (as differentiated from “off”). The microphone router includestwo main circuits: a microphone input circuit 54, replicated three timesand a microphone output circuit 56, replicated six times. A bus 58connects the circuits. In addition, a latch 60 interfaces to the MPC-565(not shown) to hold the routing information.

[0056] With reference to FIG. 6, a schematic diagram of a microphoneinput circuit 70 is illustrated, in accordance with the presentinvention. For purposes of illustration, the drawing shows switches andrelays where an alternative embodiment of the router may use solid-statecomponents. The input circuit 70 supports both transistorizedmicrophones and condenser microphones. The microphone selection is madeduring system configuration, including setting the phantom power to themicrophone (0-12vdc) and setting the gain. Each microphone 72 can beindividually configured. Moreover, the present invention contemplatessetting the configuration in hardware and/or software. A pair of 1-to-8demultiplexers 74 switches the microphone 72 to the desired output bus.One demultiplexer 74 routes the audio signal 76 onto the internal busand the other routes the PTT signal 78 onto the internal bus. Thedemultiplexers are ganged together so that the audio and PTT inputs froma microphone are routed as a pair.

[0057] With reference to FIG. 7, a schematic diagram of a microphonerouter circuit 80 is illustrated for matching router and outputcircuits, in accordance with the present invention. The circuit 80connects to the internal bus and provides a microphone level output 82that can be connected to the VACM or to a two-way radio. The outputcircuit provides both a PTT signal 84 and a balanced and isolated audiosignal 86.

[0058] The audio board requires connectors for power/ground,communication with processor, and audio input and output signals.

[0059] With reference to FIG. 8, a block diagram of an embodiment of theaudio board 14 is illustrated, in accordance with the present invention.The audio board 14 includes of four major subsystems. The only subsystemnot discussed previously is the optional processor block 92. When board14 is used as an internal interface module block 92 is depopulated sincethose functions are incorporated into the main processor board. Whenboard 14 is used as an external interface module, block 92 includes a68HC12 micro-controller or similar device and CAN interface. Together,they drive a (Serial Peripheral Interface) SPI interface to the audiomixer and microphone router. The interface looks just like the interfacethat the main processor board drives when the audio board is used as aninternal interface module.

[0060] With reference to FIG. 9, an alternate embodiment of an invehicle audio system 100 for processing a plurality of audio inputsignals 112 is illustrated, in accordance with the present invention.System 100 includes an audio board 114, a processor board 16, and anaudio output board 118. The audio board 114 includes twenty CODECs andsupporting circuitry (e.g. control logic and microphone power). Board114 receives twenty analog inputs and combines the inputs into a 32 kHzby 16 bit digital audio stream that is passed to processor board 116.Further, board 114 receives a 32 kHz by 16 bit digital audio stream fromprocessor board 116 and generates 20 analog outputs. Generally, all theinputs are identical and all the outputs are identical.

[0061] Processor board 116 includes a central processor (CP) 124 and adigital signal processor (DSP) 126. The DSP 126 does all the audioprocessing, including: mixing, routing, and array microphone signalprocessing. The processing executed by DSP 126 is controlled byconfiguration settings that CP 124 passes to DSP 126 via a hostprocessor interface (HPI). Further, CP 124 uses the HPI to downloadfirmware to DSP 126 each time the system powers up. Further, CP 124sends commands to DSP 126 during normal system operation. DSP 126controls audio board 114 (i.e. input levels, CODEC gain levels, etc.)through a serial peripheral interface (SPI). The SPI is a standardinterface supported by many micro-controllers and micro computers,including an MPC565 and 68HC112 micro controllers. Output board 118includes an audio amplifier 128 in communication with audio board 114and a plurality of speakers 130. Audio amplifier 128 amplifies the datasignals received from audio board 114 and then communicates thosesignals to the plurality of speakers 130. Speakers 130 then broadcastthe signal to a vehicle's passenger compartment. Preferably, system 100includes at least four speakers 130 and accordingly, audio amplifier 128is a four-channel audio amplifier. Further, system 100 provides enableinputs and outputs for most of the audio channels. The enable input andoutput information is passed between DSP 126 and audio board 114 via theSPI. For example, the enable inputs are typically connected topush-to-talk (PTT) signals from microphones or to the squelch outputsfor radios. System 100 generates the enable outputs using the enableinputs, internally generated voice operated transmitter (VOX) signals,and input from CP 124 as directed.

[0062] DSP 126 implements a seventeen by twenty mixer/router throughcontrol logic. Sixteen of the physical inputs are routed to the mixer.The seventeenth mixer input is reserved for a future processed audioinput that will be generated from a four array microphone inputs.

[0063] Advantageously, there are no inherent restrictions on routing,all inputs to the mixer/router can be routed to any of the outputs,along with the accompanying enable signals. Of course, a high levelcontrol software has the option of limiting certain routing combinationsbut the hardware does not enforce these restrictions.

[0064] In addition to routing audio signals to various outputs, themixer/router routes the enable signals to the appropriate enable outputsto be used for keying radios, enabling voice recognition, activating logrecording, etc. The enable signals are also used to modify the internalbehavior of the mixer, for example, prioritizing certain inputs,changing the gain of an input, or modifying the audio routing. The mixerroutes the enable signals in a similar manner to and with the sameflexibility as it routes the audio signals. Any input enable signal canbe used anywhere in the mixer.

[0065] Devices such as a two-way radio 132 have both inputs 134 andoutputs 136 associated with them, however, from an internal routingperspective, the inputs 134 and outputs 136 are treated as separateentities. Although the connector strategy may imply that certain pairsof inputs 134 and outputs 136 belong to the same device, the actualrelationship of input 134 to output 136 is totally under the directionof the high level software.

[0066] In embodiment of the present invention, multiple inputs areassigned to a signal output. In this case, control software is providedfor designating one or more inputs as priority inputs which would resultin a dimming (reduction in volume) or completely turning off the otherinputs. Further, some devices require a signal at all times. Forexample, a voice recognition system continuously tracks the ambientnoise levels. However, other devices only require noise signal to bepresent when a corresponding enable signal is active. The mixing/routerof the present invention support both functions.

[0067] Further, the present invention provides a mixer/routerimplemented by DSP 126 and designed to support the functions shownbelow. Processor 124 sets up the following functions when required bychanging DSP's low level control information. After the low levelcontrol information is set by processor 124, DSP 126 will perform thefollowing functions without processor 124 interaction. By keepingprocessing 124 out of the loop, the mixer/router of DSP 126 respondsmore quickly to changes in the audio inputs. Some of the functionssupported by DSP's mixer/router are:

[0068] a) Routes two-way radio audio to a public address speaker;

[0069] b) Create a cross-band mobile repeater to assist communicationbetween hand-held radio and dispatch (for example, by interconnecting150 mHz radio and a 450 mHz radio to the mixer to function as a mobilerepeater);

[0070] c) Provide a mobile command post function by using a multipleradios to connect different agencies or sources on different radiobands;

[0071] d) Use a single hands-free microphone to work with both a voicerecognition and two-way radio by selecting the appropriate PTT switch(i.e. one switch for voice recognition, another for the radio);

[0072] e) Log conversations and other communication using the vehicle'srecorder system;

[0073] f) Set the apparent spatial location of each radio within thevehicle compartment using speakers 130; and

[0074] g) Use a hands-free microphone operating in VOX mode with thedispatch two-way radio while the vehicle is operating.

[0075] Audio inputs 136 are specific as to their function. Microphoneinput and line and speaker inputs are provided, and because ofelectrical differences, six different types of input circuits areprovided. For example, a general purpose input having an input voltageranging from 80 mV to 5 volts RMS with a PTT is provided. Inputimpedance is at least 10 K Ohms. A swamping resister may be placedacross a line to function as a speaker load.

[0076] General purpose high level inputs work from 400 mV to 25 voltsRMS without PTT. Input impedance is at least 10 K Ohms. This input isfor exceptionally high level input signals such as a siren driveramplifier.

[0077] Speaker inputs work from 160 mV to 10 volts RMS, no PTT. Inputimpedance is at least 10 K Ohms. Again, a swamping resister may beplaced across the line to function as a speaker load. Speaker inputs aredesigned to handle high output signals that would overpower a generalpurpose input.

[0078] A hand-held microphone input is provided to work with standardtransistorized carbon microphone and having a 12 volt bias voltage. Themicrophone input supports PTT. The microphone's impedance is 600 Ohms. Ahand-held microphone is 16 mV to 1 volt with PTT; a wireless microphoneis 80 mV to 5 volts with PTT and a hands-free microphone is 80 mV to 5volts but with no PTT. Input impedance is at least 10 K Ohms. Arrayelement microphone inputs work identical to standard microphone inputexcept that they do not support PTT.

[0079] Each input 136 has a gain control that may be set by processor124. Processor 124 sets the overall input sensitivity range which may beeither a positive or negative gain value (using a db scale). The gain isachieved using a programmable gain feature of the CODEC, and analog gainsection before the CODEC and the digital gain applied to the DSP. Table3 below shows an assignment of physical input signals along with theproperties of the individual inputs, in accordance with an embodiment ofthe present invention. TABLE 3 Channel Purpose Type 1 Radio 1 GP 2 Radio2 GP 3 Radio 3 GP 4 Radio 4 GP 5 Radio 5 GP 6 Radar (Doppler signal) GP7 Spare GP 8 Spare GP 9 AP GP 10 Wireless Microphone GP 11 HandheldMicrophone Mic. 12 Handsfree Microphone GP 13 VACM Responses GP 14Reserved for siren driver signal for noise GPH cancellation 15 AM/FMTuner Left Channel Speaker 16 AM/FM Tuner Right Channel Speaker 17Reserved for array microphone element 1 Array Mic. Element 18 Reservedfor array microphone element 2 Array Mic. Element 19 Reserved for arraymicrophone element 3 Array Mic. Element 20 Reserved for array microphoneelement 4 Array Mic. Element

[0080] The mixer implemented in DSP 126 has an input 138 which carriesthe digital information from the CODEC's 120 to DSP 126. Each of themixer inputs 138 have a gain control that is used to fine tune andnormalize the input signal. The mixer normalizes the inputs to minimizedistortion and to avoid overdriving a radio transmitter which wouldcause it to operate incorrectly. Each input 138 is capable of generatingan enable signal. The enable signal can be generated using anycombination of the following inputs:

[0081] 1) An external enable input, usually generated by the attacheddevice using a “dry contact” such as a microphone push-to-talk switch ora radio generated squelch open signal;

[0082] 2) An internal voice operated transmitter (VOX) signal generatedby DSP 126 to indicate the presence of audio on the input channel; or

[0083] 3) A processor enable is generated by software running onprocessor 24.

[0084] Each mixer input 138 is configured to use any or none of theenable signals. If multiple enable signals are selected, then they arelogically or'ed together (any one of the enable signals will activatethe enable output).

[0085] With the exception of the four speaker outputs, all audio outputshave an associated output enable signal which is in the form of a drycontact. The outputs specified for the two-way radios each have ahardware timer on the PTT output that times out after four minutes. Themonaural outputs are settable from microphone output levels up through a600 Ω 0 dB ceiling at line level. DC blocking is required on allmonaural outputs. Table 4 below shows an assignment of the outputsignals, in an embodiment of the present invention. TABLE 4 SignalPurpose Type 1 Two-way radio 1 Monaural with PTT + HW timer 2 Two-wayradio 2 Monaural with PTT + HW Timer 3 Two-way radio 3 Monaural withPTT + HW Timer 4 Two-way radio 4 Monaural with PTT + HW Timer 5 Two-wayradio 5 Monaural with PTT + HW Timer 6 Spare Monaural with PTT 7 SpareMonaural with PTT 8 VCR Monaural with PTT 9 Spare Monaural with PTT 10Spare Routed to internal expansion connector 11 Spare Routed to internalexpansion connector 12 Spare Routed to internal expansion connector 13VACM Monaural with PTT 14 PA system (siren Monaural with PTT amplifier)15 Spare Routed to internal expansion connector 16 Spare Routed tointernal expansion connector 17 Stereo Left Front To internal Amplifier18 Stereo Right Front To internal Amplifier 19 Stereo Left Rear Tointernal Amplifier 20 Stereo Right Rear To internal Amplifier

[0086] Referring now to FIG. 10, a general purpose input channel 150 isillustrated, in accordance with the present invention. Input channel 150includes an audio input (analog) 152 and an enable input (discrete) 154.Two outputs, audio and enable are generated and used internally withinthe mixer/router of DSP 126. Both outputs 156 and 158 are digital. Audioinput signal 152 may be either line level or speaker level. Further, theaudio input signal 152 is processed by a gain control stage 160 in CODEC20 which is reflected in the digitized output 156. Enable input 154 maycome from for example a microphone pushed-to-talk switch or a squelchopen indication from a two-way radio. Further, an input enable signalmay be generated by the input channel and configured to come from anycombination of: an external device, an internally generated VOX signal,a combination of a VOX signal and an external device, or directly drivenby processor 124.

[0087] All the switches shown in FIG. 10 are, in an embodiment,registers in DSP 126 or latches on audio board 114. Processor 124 setsthe DSP registers directly via the HPI interface. Processor 124 sets thelatches on audio board 114 by setting registers in DSP 126. DSP 126 thenpropagates the audio board 114 via the SPI interface. Gain and levelsettings 162 and 164 (i.e. the CODEC gain setting or VOX thresholdsetting) are also registers. Processor 124 controls gain and levelsettings 162 and 164 in a like manner as switches.

[0088] Mixer of DSP 126 provides 20 outputs. Any input 138 can be routedto any output. Multiple inputs may be assigned to a single output inwhich case they will be mixed accordingly to their gain settings. System100 automatically calculates gain settings so that multiple inputs donot override an output. System 100 further provides an automaticcompression system so that the output level can be set to be heard whenonly one channel is active and not be driven into distortion when theremaining inputs go active at the same time. Using the enable signalsone or more inputs may be assigned a priority allowing an input to takeover a channel when the enable signal becomes active. For example, eachoutput can be assigned its own set of priority inputs. The priorityinputs may enable the other inputs on an input by input basis.Generally, no more than one input will be designated a priority inputfor each output channel. For example, the input enable signal may beused internally to disable the output even when the input audio is notenabled for that output.

[0089] Each output has for example, all seventeen enable signalsavailable with the ability to ignore or mask out enable signals that arenot related to the output. Additionally, each output has a processor 124controlled enable signal. The processor controlled enable signal has ahigher priority than the other enable signals, such that when theprocessor enable signal is commanding the output on, the output is onregardless of the other enable signal. Each output enable has theconfigurable setting that permits it to be in one of the followingstates: always on, always off, follow the input enable signals, andfollow only the processor enable signal. The enable signal for example,may be sent to an output device to activate a transmitter, start a login device, or enable voice recognition.

[0090] In an embodiment of the present invention microphone inputs areprovided. The microphone inputs are general-purpose inputs withdifferent initial gain settings. In addition, a handheld microphoneinput (a specially designated channel) supports a powered microphonewith a +12V power signal imposed on the microphone audio input signal.The handheld microphone input supports both standard dynamic microphonesand standard “transistorized” amplified microphones that mimic carbonmicrophones. The hands free microphone input is also specialized in thatit supplies a DC voltage of at least 9.0V at a current of at least 100mA for powering the external hands free microphone electronics.

[0091] Of the twenty physical inputs, sixteen are directly connected tothe mixer. The remaining four inputs, the array microphone elements, aremade available for future array microphone processing. The 17^(th) inputof the mixer is reserved for the output of the array microphonealgorithm. The mixer/router mixes and routes both audio signals andenable signals (PTT output).

[0092] Advantageously, the audio portion of the mixer/router can mix anycombination of the input audio channels into each output channel.Processor 24 is responsible for communicating to DSP 126 what level ofeach input signal should be mixed into each output signal. If the mixlevel is set to zero, the corresponding input channel is not included inthe output signal.

[0093] Processor 124 is capable of specifying two sets of mixing levelsfor each output channel. The two levels can be used in various ways. Forexample, the speaker output channels can be set up with one setting fornormal listening and a second setting that dims the AM/FM tuner, etc.when the user presses the push to talk switch for a microphone.

[0094] With reference to FIG. 11, there is illustrated an audio routinglogic 200 for an output channel. The audio routing logic determineswhich of two sets of mixer levels to use at any moment in time. Eachoutput channel has its own copy of this logic with the associatedconfiguration switches. Output 202 of circuit 200 determines which ofthe two sets of mixer levels will be used to generate an audio output.

[0095] The input configuration switches 204 determine which inputs areused to calculate the Audio Routing Enable signal for a given outputchannel. CP Enable logic 206 determines whether the CP 124 controls theoutput, overriding the enable calculation. Force control logic 208allows a second level of override, which is used primarily for debuggingpurposes.

[0096] With reference to FIG. 112, a PTT Enable Signal Logic 300 isillustrated. PTT signal for each output is generated. Each output hasits own copy of logic 300 along with the associated configurationswitches 302 and controls.

[0097] PTT Enable Signal Logic 300 is similar to its audio counterpart,with the addition of a watchdog timer 304 and the ability to completelydisable the output.

[0098] Input configuration switches 302 (implemented as a register inDSP 126) selects which inputs are part of the calculation that generatesthe enable signal output. The next logic section 306 selects whether theCP or the Input Enables controls the PTT logic. It is followed by forcelogic 308 to hold the PTT on or off always. Then the PTT watchdog timer304, mandated by the FCC, makes it impossible to hold a radio in key oncondition for more than three minutes. The watchdog timer section 304 isonly present on outputs that act as microphone inputs to two-way radios.Then the PTT output can optionally be disabled or inverted.

[0099] The PTT watchdog timer may need to be implemented in hardware asa separate device if FCC requirements dictate hardware-based fail-safedevices.

[0100] The mixer/router supports two kinds of outputs: monaural andspeaker. The monaural outputs drive two-way radios, logging devices,etc. The speaker outputs drive the four speakers in the vehiclepassenger compartment.

[0101] With reference to FIG. 13, an audio routing 350 for a singleoutput channel is illustrated. Each output has its own Audio RoutingEnable Signal Logic (see FIG. 11). Seventeen pairs of gains 352, anenabled and a disabled setting 354 for each input 356

[0102] Each output has an automatic gain control circuit (AGC) 358 thatlimits the level passed on to the external device. The primary functionof the AGC circuit 358 is to allow the system to have multiple outputsactive at the same time and to maintain the average audio output level,regardless of how many outputs are producing audio at a given time.Although the AGC does, in fact, compress the audio signal, it is notintended to be used as a full-fledged compressor because that wouldrequire running the normalized signals “hot”, which in turn will causethe mixer to distort the output.

[0103] The final step in the output processing is to be able to set theoutput level. Speaker outputs have the same audio processing capabilityas monaural outputs (see FIG. 13), but they serve a particular purpose.By including four speaker outputs it is possible to assign both thelevel of an input channel in the vehicle, and where in the passengercompartment the signal appears to originate. The ability to assign inputsignals to different spatial locations eases the listeners' auditoryburden when multiple audio sources are present simultaneously.

[0104] As any person skilled in the art of systems and methods forrouting audio signals in automobiles will recognize from the previousdetailed description and from the figures and claims, modifications andchanges can be made to the preferred embodiments of the inventionwithout departing from the scope of this invention defined in thefollowing claims.

1. An audio signal processing system for a vehicle, the vehicle having aplurality of audio output producing devices, the system comprising: anaudio input circuit for receiving a plurality of audio signals from theplurality audio output producing devices; a processor in communicationwith the audio input circuit for combining the plurality of audiosignals; an audio output circuit in communication with the audio inputcircuit for receiving the combined plurality of audio output signals,wherein the audio output circuit conditions the plurality of audiosignals for output; and at lease one speaker for broadcasting theconditioned plurality of audio signals to a vehicle occupant.
 2. Thesystem of claim 1 wherein the audio input circuit further comprises aplurality of analog to digital converters.
 3. The system of claim 1wherein the audio input circuit further comprises a plurality of CODECS.4. The system of claim 3 wherein the audio input circuit comprisestwenty CODECS.
 5. The system of claim 1 wherein the processor furthercomprises a digital signal processor.
 6. The system of claim 1 furthercomprising four speakers.
 7. The system of claim 1 further comprising atleast one microphone.
 8. The system of claim 1 wherein the audio outputcircuit further comprises an audio amplifier.
 9. The system of claim 1wherein the audio input circuit further comprises a microphone routercircuit for directing a plurality of microphone inputs to a plurality ofaudio equipment.
 10. The system of claim 1 wherein the audio outputcircuit further comprises an audio mixer for receiving the plurality ofaudio signals and directing the plurality of audio signals to the properoutput device.
 11. An audio signal processing system for a vehicle, thevehicle having a plurality of audio output producing devices, the systemcomprising: an audio input circuit for receiving a plurality of audiosignals from the plurality audio output producing devices; a processorin communication with the audio input circuit for combining theplurality of audio signals; a voice activated control circuit incommunication with the processor for controlling a processor operation;an audio output circuit in communication with the audio input circuitfor receiving the combined plurality of audio output signals, whereinthe audio output circuit conditions the plurality of audio signals foroutput; and at lease one speaker for broadcasting the conditionedplurality of audio signals to a vehicle occupant.
 12. The system ofclaim 11 wherein the audio input circuit further comprises a pluralityof analog to digital converters.
 13. The system of claim 11 wherein theaudio input circuit further comprises a plurality of CODECS.
 14. Thesystem of claim 13 wherein the audio input circuit comprises twentyCODECS.
 15. The system of claim 11 wherein the processor furthercomprises a digital signal processor.
 16. The system of claim 11 furthercomprising four speakers.
 17. The system of claim 11 further comprisingat least one microphone.
 18. The system of claim 11 wherein the audiooutput circuit further comprises an audio amplifier.
 19. The system ofclaim 11 wherein the audio input circuit further comprises a microphonerouter circuit for directing a plurality of microphone inputs to aplurality of audio equipment.
 20. The system of claim 11 wherein theaudio output circuit further comprises an audio mixer for receiving theplurality of audio signals and directing the plurality of audio signalsto the proper output device.
 21. A method for processing audio signalsfor broadcasting in a vehicle, the vehicle having a plurality of audiooutput producing devices, the method comprising: receiving a pluralityof audio signals from the plurality of audio output producing devices;combining the plurality of audio signals using a processor; receivingthe combined plurality of audio output signals using an audio outputcircuit, wherein the audio output circuit conditions the signals foroutput; and broadcasting the conditioned plurality of audio signals to avehicle occupant using at lease one speaker.